The present invention relates generally to a pulsed current monitor and more particularly to an in-line monitor for measuring the beam current pulse of an intense relativistic electron beam (IREB).
Intense relativistic electron beams are useful for applications in fusion and plasma physics research, X-ray production for radiography, electron beam physics research, beam propogation studies, collective ion acceleration, material science, laser physics, and, especially, electron beam accelerator technology. Although suitable monitors have existed for low current beams in vacuum transport lines, previous monitors could not accurately characterize fast rising, high current, beam pulses in gas transport lines without physically stopping the beam. If the beam is stopped, it is not available further down-stream for experiments. A Faraday cup monitor is one such prior art device for measuring these high current electron beams.
IREB current is the flow of high energy electrons (energy greater than 100 KeV). This current is difficult to measure in gas neutralized transport lines which propagate an IREB because these lines also have high plasma currents due to the flow of low energy plasma electrons being released by gas ionizations. These currents may interfere with the desired beam current measurements. Previous in-line monitors in gas neutralized beam transport lines, such as the monitor shown in U.S. Pat. No. 4,438,394 by one of the inventors, measure net current (I.sub.n), which current is the sum of the beam current I.sub.b plus the plasma current I.sub.p. However, in order to provide an accurate measurement of beam current, a way is needed to separate I.sub.b from I.sub.p without stopping the beam.